A ministry is a specialised organisation
responsible for a sector of governmentpublic administration, sometimes
led by a minister, but usually a senior public
servant, that can have responsibility for one or more
departments, agencies, bureaus, commissions or other smaller
executive, advisory, managerial or administrative
organisations.

Canada

In Canada, some
provincial-level government departments are called "ministries"
(such as in Ontario, British
Columbia, and Alberta)
but most, along with their federal analogues, are termed
"departments." Their heads are referred to as "ministers" in both
levels of government, however. The specific tasks assigned to a
minister is referred to as his or her "portfolio".

New
Zealand

New Zealand's
state agencies include a large number of ministries and a somewhat
smaller number of departments. Increasingly, state sector agencies
are styled neither as ministries nor as departments. All New
Zealand agencies are under the direction of one or more ministers
or associate ministers, whether they are styled "ministries" or
not, though each body also has an apolitical chief executive. In
ministries and departments, these chief executives are often called
Secretaries.

In Canada, some provincial-level government departments are called "ministries" (such as in Ontario and British Columbia) but most are called "departments." Their heads are referred to as "ministers" in both levels of government, however.